The disclosure of the following priority application is incorporated herein by reference in its entirety: Japanese Patent Application No. 2000-109833 filed Apr. 11, 2000.
1. Field of Invention
This invention relates to a stage device in which a stage main body holding an object moves within a plane over a base, and to an exposure apparatus that performs an exposure process using a substrate held as the object on this stage device. In particular, the invention relates to a stage device and an exposure apparatus using a lithography process to manufacture a micro-device, such as, e.g., a liquid crystal display device or a semiconductor device.
2. Description of Related Art
Conventionally, various exposure apparatus are used to fabricate a semiconductor device, a liquid crystal display device, or the like by a photolithographic process. Recently, as exposure apparatus for fabricating a liquid crystal display panel (LCD panel) have become large, a unity-magnification batch transfer method in which exposure is possible over a large area or a step-and-scan type scanning projection exposure apparatus have been widely used.
In a step-and-scan type exposure apparatus for fabricating, for example, a liquid crystal display device, a reticle (mask) and a glass substrate are respectively held by stage devices. The reticle and the glass substrate are simultaneously, synchronously moved in one direction (the scanning direction) with respect to a projection optical system, and a reticle pattern is projected and exposed to each shot region on the glass substrate via the projection optical system.
FIG. 14 is an external perspective view showing one example of this type of stage device.
A stage device 1 shown in FIG. 14 is schematically constituted by a base (table) 2 that is supported by four vibration control pads 9, a stage (stage main body) 4 that is guided by an air guide 3 arranged on the base 2 and is freely moved in a Y-direction, which is the scanning direction, and a linear motor 5 that is controlled to drive the stage 4 in the Y-direction.
The linear motor 5 is constituted by linear motor movable parts 6 that protrude from both sides of the stage 4 in the X-direction, and linear motor stationary parts 8, having a U-shaped cross-section, arranged at a predetermined interval from each other in the X-direction so as to sandwich the respective movable parts 6. The stationary parts are arranged on reaction frames 7. The stage 4 is driven as the movable parts 6 move in the Y-direction due to a thrust generated between the movable parts 6 and the stationary parts 8, in a state that maintains a predetermined gap size with respect to the stationary parts 8,. Furthermore, the reaction frames 7 are vibrationally isolated from the base 2. Accordingly, the reaction force generated by acceleration and deceleration of the stage 4 is transmitted to the reaction frames 7 via the stationary parts 8. The provision of the reaction frame(s) prevents vibration of the stage 4 and of a projection optical system (not shown), which is mounted to the base 2, and prevents positional discrepancy of a reticle or a glass substrate held on the stage 4 because the reaction force is not transmitted to the base 2.
Furthermore, when the stage 4 moves, a position of the center of gravity of the stage device 1 changes. This causes a load applied to each of the vibration control pads 9 to change, such that a different load is applied to each of the vibration control pads 9. Because of this, the base 2 can become inclined because a height of each of the vibration control pads 9 is not the same (they are not equal to each other).
Meanwhile, even if the stage 4 moves and the base 2 is inclined, the stationary part 8 on the reaction frame 7 is not inclined (because it is mounted on the reaction frame 7). Therefore, there is a possibility that changes may occur in the size of the gap between each movable part 6 and its respective stationary part 8 such that these two parts may contact each other. Therefore, conventionally, when unequal loads are applied to the vibration control pads 9, in order to constantly maintain the base 2 in a horizontal orientation, an active type vibration control pad, having, for example, a voice coil motor, needed to be used. Such active type vibration control pads applied a counter-force to the base 2 in order to maintain the base horizontal.
However, the following problems exist in a conventional stage device and exposure apparatus having an active type vibration control pad system.
An active type vibration control pad system is provided with, for example, an air mount with a controllable internal pressure, or an actuator such as a voice coil motor, a piezoelectric element, or the like. In addition, the system is structured so as to control a posture of the base 2 by driving the voice coil motor or the like based on, for example, measurement values obtained from six accelerometers fixed to a main frame.
Conventionally, six degrees-of-freedom active control is performed, and four or more support points (pads) are provided for the vibration control pad system. Because the stage device is very heavy, the control pad system must withstand a load of several tons. Thus, in addition to having a complicated structure of the vibration control pad itself compared to the passive type, there are problems such that various devices such as an accelerator, a controller, and the like are needed. This causes the price of the vibration control pad system to be very high. Additionally, the amount of tooling for arrangement and adjustment increases, so there is also a problem in that the cost of the stage device and the exposure apparatus significantly increases. Additionally, due to effects of floor movement characteristics, there also is a problem of instability of movement.
Meanwhile, in the linear motor 5 that drives the stage 4, it has been determined that a unique fluctuation, which is called xe2x80x9cthrust ripplingxe2x80x9d, included in thrust, can significantly affect positionxc2x7speed controllability of the stage 4. This thrust rippling is a function of the driving thrust generated by a driving amplifier, viscosity generated by the linear motor, the amplitude which is unique to individual linear motors, and the like. Recently, by considering the affect of thrust rippling, the driving of the linear motor is appropriately controlled so as to cancel the effects of thrust rippling.
However, in the linear motor 5, a change in the size of a gap between the movable part 6 and the stationary part 8 (as described above) also changes the thrust rippling. Therefore, even if thrust rippling that is initially generated is considered and the driving of the stage is appropriately controlled, a predetermined control capability cannot be obtained, and there is a possibility that there may be a negative effect on positionxc2x7speed controllability of the stage.
This invention reflects on the above-mentioned problems. An object of this invention is to provide a stage device and an exposure apparatus that do not cause any problems such as deterioration of stage control capability, contact between a stationary part and a movable part, or the like, even if an inexpensive passive type of vibration control pad system is used.
A stage device according to one aspect of this invention includes a stage main body that moves on a base and a support that is vibrationally isolated from the base. The stage device includes a movable part disposed on the stage main body that moves relative to a stationary part that is supported by the support. A detector detects the size of a gap between the movable part and the stationary part, and an actuator adjusts a relative positional relationship between the stationary part and the movable part based on the detected size of the gap. The stage device can hold a mask (reticle) and/or a substrate (glass plate, semiconductor wafer, etc.).
In the stage device according to this aspect of the invention, as the stage main body moves on the base, if the base is inclined, the stage main body and the movable part are also inclined. However, because the stationary part is supported by the support, which is vibrationally isolated from the base, a size of the gap between the movable part and the stationary part changes. However, if this change in gap size is detected by the detector, the actuator can be controlled to adjust a relative positional relationship between the movable part and the stationary part, and the size of the gap therebetween can be returned to a predetermined value.
If the detector is disposed on the stationary part, the gap size needs to be detected by disposing detectors in a movable range of the movable part. Therefore, it is preferable that the detector is disposed on the movable part. Additionally, because the weight of the stationary part is approximately several tens of kilograms, whereas the weight of the stage main body including everything it is supporting is approximately several hundred kilograms, it is preferable that the actuator drives the stationary part.
The stage device can be used in an exposure apparatus in which the stage device is used as a mask stage or as a substrate stage. The exposure apparatus also could use one stage device of this invention as a mask stage and another stage device of this invention as a substrate stage.
Therefore, in an exposure apparatus according to one aspect of this invention, prior to performing exposure, when at least one of the mask stage and the substrate stage moves, even if the bases are inclined and a gap size between the movable parts and the stationary parts changes, actuators adjust a relative positional relationship between the movable parts and the stationary parts, and a gap size between these elements can be returned to a predetermined value.